After the trophy-laden years of Alex Ferguson's reign, the appointment of David Moyes as his successor failed to yield the desired results for the United fans and board alike.
Moyes departed in April, with the club languishing in seventh, having lost almost a third of their Premier League matches under the Scot.
Their eventual seventh-placed finish was their lowest in the league since ending the 1989-90 campaign in 13th position and, below, we look at areas that Van Gaal will need to address if he is to return the club to winning ways.
Find a consistent central defensive partnership
With Rio Ferdinand and Nemanja Vidic set to leave the club, a gaping hole has been left in the United backline. The duo developed a formidable partnership for United over the years and, despite playing less regularly together due to injuries in recent times, still looked to be United's strongest pairing. The likes of Chris Smalling and Phil Jones show potential, but too often this season United's selection at the heart of the defence was altered from game to game, and that inconsistency contributed to their downfall.
Replace the experience and leadership leaving the club
Along with the departures of Ferdinand and Vidic, Ryan Giggs' retirement to take on the role of assistant manager under Van Gaal and Patrice Evra's expected exit means the squad will be shorn of a wealth of experience. Van Gaal needs to bring in senior professionals who will lead by example on the field, and to take some of the burden off Wayne Rooney and Robin van Persie. The great United teams over the past two decades were littered with players of strong character and vast experience in the game, and Van Gaal needs to restore that calibre to his squad.
Buy a dynamic midfielder
United's midfield was criticised for being too one-paced this season, with the likes of Michael Carrick, Tom Cleverley and Marouane Fellaini all coming under fire for ponderous displays. In the past, United's game was based on fast, attacking football, and Van Gaal must bring someone in who can break from midfield and drive the team forward at pace.
Use Giggs' extensive knowledge to his advantage
Confirmation of Giggs as the Dutchman's assistant manager was no great surprise, and Van Gaal needs to utilise the 40-year-old as best he can. Giggs has spent the last 24 years at Old Trafford, even managing the club at the end of this season, and knows the club better than anyone. Van Gaal would be wise to tap into that knowledge and ensure the club move forward while sticking to the principles that have made it one of the best in the world.
Find a way to get the best out of Mata, Van Persie and Rooney
Juan Mata's arrival from Chelsea in January raised hopes of a revival in the second half of the season among United fans - a recovery which never quite materialised. Although the Spaniard showed flashes of brilliance, he was often used in wide areas, away from a central position where he could influence the game more tellingly. As the three outstanding players in the squad, Van Gaal needs to figure out a way to use Mata, Van Persie and Rooney in the same system, without the trio getting in each other's way.
